As shown in FIGS. 1A, 1B and 1C, a typical cupola 10 is a cylindrical shaft furnace that burns coke, ore or scrap steel and limestone, intensified by the blowing of air through tuyeres, shown at 11, to create a molten metal or alloy such as iron. Slags are also created along with the metal or alloy as a result of the smelting of ore. Alternate layers of ore, limestone and coke are charged into the top of the cupola. A charger is shown at 13. As the ore descends, the ore is melted by direct contact with the countercurrent flow of hot gases from the coke combustion. The resulting molten metal or alloy collects in the well of the cupola where it is discharged for use by intermittent tapping or by continuous flow. The slag, being lighter than the metal or alloy, rises to the top of the tapped mixture. The slag is skimmed off the top of the molten metal or alloy after the mixture is discharged through the tap hole.
In a dry bottom cupola, the metal or alloy and slag are not collected in the well of the cupola but are forced by blasts of air into a special vessel outside and beside the cupola to separate the slag from the metal or alloy. Such a separator is shown at 15 in FIG. 1A. Inside the separator the slag rises to the top of the molten metal or alloy. The slag is then siphoned off through a slag exit hole which is maintained about 2-3 inches higher than a metal or alloy exit hole. The conventional slag separator consists of one chamber which receives the molten metal or alloy and slag. The metal or alloy typically exits onto a launder 14 as shown in FIGS. 1B and 1C leading to a holding furnace 17 as shown in FIG. 1C.
The conventional slag separator, however, when used with a dry bottom cupola fails to remove all of the slag from the metal or alloy due to the turbulent stirring of the metal or alloy. As a result, the final product exiting from the conventional slag separator is not in a highly purified form. It is therefore a problem in the prior art to easily and completely separate metal or alloy, such as iron, from its slag.
In addition, due to the high temperature of the molten metal or alloy and slag, the conventional separator must be lined with a refractory to protect the separator against abrasion, heat and oxidation. It is a problem, however, that there is a great deal of mechanical and chemical attack on the refractory especially at the outlet from the cupola. As a result, the refractory wears out and must frequently be torn down, at least every two to five weeks, and the separator relined. This is not only costly but time consuming leading to a considerable amount of down time during which the cupola and its separator cannot be used. Thus, it is also a problem to provide a separator which does not require frequent replacement of the refractory or significant down time.
Moreover, the use of hot air to force the molten metal or alloy and slag into the separator prevents the operator from removing the top of the separator to inspect the state of the refractory and to make spot repairs. The top must remain in place to protect the operator from the hot air. Accordingly, inspection and repairs must be made when the separator is not running resulting in additional down time. Thus, it is also a problem in the prior art to provide a separator which can be opened and repaired by the operator while in use.